Currently what is the best Firewall & Internet security for Ubuntu?
Ubuntu has an inbuilt firewall caled
The graphical version for it is
gufw. Search in the Ubuntu Software Center you will find it
Ufw is installed by default and is one of the strongest firewalls ever
See this Ubuntu Documentation for Firewalls
Regarding an Antivirus software, you dont need one because linux rarely catches a virus.
There are hardly any linux viruses
If you insist on having one for windows files on linux,
Clamav found in the Ubuntu Software Center and the gui frontend for it is
clamtk also found in the Ubuntu Software Center.
Check these Ubuntu documentations for more info
Also see this